Production of soluble soy protein product (“S704”)

ABSTRACT

A soy protein product is obtained by extracting a soy protein source material with an aqueous calcium salt solution to form an aqueous soy protein solution and adjusting the pH of the mixture of aqueous soy protein solution and residual soy protein source to a pH of about 1.5 to about 4.4. The acidified soy protein solution then is separated from the residual soy protein source. The acidified soy protein solution may be dried, following optional concentration and diafiltration, to provide the soy protein product.

REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 USC 119(e) from U.S.Provisional Patent Application Nos. 61/457,721 filed May 19, 2011 and61/457,815 filed Jun. 9, 2011.

FIELD OF INVENTION

The present invention is directed to the production of soy proteinproducts.

BACKGROUND TO THE INVENTION

In U.S. patent application Ser. No. 12/603,087 filed Oct. 21, 2009 (USPatent Publication No. 2010-0098818) and Ser. No. 12/923,897 filed Oct.13, 2010 (US Patent Publication No. 2011-0038993), assigned to theassignee hereof and the disclosures of which are incorporated herein byreference, there is described the preparation of a soy protein product,preferably a soy protein isolate, which is completely soluble and iscapable of providing transparent and heat-stable solutions at low pHvalues. This protein product may be used for protein fortification of,in particular, soft drinks and sport drinks, as well as other acidicaqueous systems, without precipitation of protein. The soy proteinproduct is produced by extracting a soy protein source with aqueouscalcium chloride solution at natural pH, optionally diluting theresulting aqueous soy protein solution, adjusting the pH of the aqueoussoy protein solution to a pH of about 1.5 to about 4.4, preferably about2.0 to about 4.0, to produce an acidified clear soy protein solution,which may be optionally concentrated and diafiltered prior to drying.

SUMMARY OF INVENTION

It has now been found that soy protein products of similar properties tothose produced according to the above-noted applications can be preparedif the optional dilution and acidification steps are effected prior toseparation of the soy protein solution from the residual soy proteinsource material.

However, unlike the soy protein product produced as described in theaforementioned applications, the product produced in accordance with thepresent invention has a notable phytic acid content which may beresponsible for the somewhat inferior solution properties exhibited bythe soy protein product produced herein in comparison to the soy proteinproduct produced in the aforementioned applications.

In accordance with one aspect of the present invention, there isprovided a process of producing a soy protein product having a soyprotein content of at least about 60 wt % (N×6.25) on a dry weightbasis, which comprises:

-   -   (a) extracting a soy protein source with an aqueous calcium        chloride solution to cause solubilization of soy protein from        the protein source and to form an aqueous soy protein solution,    -   (b) optionally diluting the mixture of aqueous soy protein        solution and residual soy protein source,    -   (c) adjusting the pH of the mixture of aqueous soy protein        solution and residual soy protein source to a pH of about 1.5 to        about 4.4, preferably about 2 to about 4,    -   (d) separating the acidified aqueous soy protein solution from        the residual soy protein source,    -   (e) optionally concentrating the acidified aqueous soy protein        solution while maintaining the ionic strength substantially        constant by using a selective membrane technique,    -   (f) optionally diafiltering the concentrated soy protein        solution, and    -   (g) optionally drying the concentrated soy protein solution.

The soy protein product preferably is an isolate having a proteincontent of at least about 90 wt %, preferably at least about 100 wt %,(N×6.25) d.b.

The present invention further provides a soy protein product, preferablya soy protein isolate, which is water soluble and forms heat stablesolutions at acid pH values and is useful for the protein fortificationof aqueous systems, including soft drinks and sports drinks. The soyprotein in the product is not hydrolyzed.

The soy protein product provided herein may be provided as an aqueoussolution thereof having an acceptable degree of clarity at acid pHvalues and which is heat stable at these pH values.

The soy protein product can be blended with powdered drinks for theformation of aqueous soft drinks or sports drinks by dissolving the samein water. Such blend may be a powdered beverage.

While the present invention refers mainly to the production of soyprotein isolate, it is contemplated that soy protein products of lesserpurity may be provided having similar properties to the soy proteinisolate. Such lesser purity products may have a protein concentration ofat least about 60% by weight (N×6.25) d.b.

In another aspect of the present invention, there is provided an aqueoussolution of the soy product provided herein which is heat stable at lowpH. The aqueous solution may be a beverage.

The soy protein product produced according to the process herein lacksthe characteristic beany flavour of soy protein products and issuitable, not only for protein fortification of acid media, but may beused in a wide variety of conventional applications of protein products,including but not limited to protein fortification of processed foodsand beverages, emulsification of oils, as a body former in baked goodsand foaming agent in products which entrap gases. In addition, the soyprotein product may be formed into protein fibers, useful in meatanalogs and may be used as an egg white substitute or extender in foodproducts where egg white is used as a binder. The soy protein productmay also be used in nutritional supplements. The soy protein product mayalso be used in dairy analogue products or products that are dairy/soyblends. Other uses of the soy protein product are in pet foods, animalfeed and in industrial and cosmetic applications and in personal careproducts.

GENERAL DESCRIPTION OF INVENTION

The initial step of the process of providing the soy protein productinvolves solubilizing soy protein from a soy protein source. The soyprotein source may be soybeans or any soy product or by-product derivedfrom the processing of soybeans, including but not limited to soy meal,soy flakes, soy grits and soy flour. The soy protein source may be usedin the full fat form, partially defatted form or fully defatted form.Where the soy protein source contains an appreciable amount of fat, anoil-removal step generally is required during the process. The soyprotein recovered from the soy protein source may be the proteinnaturally occurring in soybean or the proteinaceous material may be aprotein modified by genetic manipulation but possessing characteristichydrophobic and polar properties of the natural protein.

Protein solubilization from the soy protein source material is effectedmost conveniently using calcium chloride solution, although solutions ofother calcium salts, may be used. In addition, other alkaline earthmetal compounds may be used, such as magnesium salts. Further,extraction of the soy protein from the soy protein source may beeffected using calcium salt solution in combination with another saltsolution, such as sodium chloride. Additionally, extraction of the soyprotein from the soy protein source may be effected using water or othersalt solution, such as sodium chloride, with calcium salt subsequentlybeing added to the aqueous soy protein solution produced in theextraction step. Precipitate formed upon addition of the calcium salt isremoved prior to subsequent processing.

As the concentration of the calcium salt solution increases, the degreeof solubilization of protein from the soy protein source initiallyincreases until a maximum value is achieved. Any subsequent increase insalt concentration does not increase the total protein solubilized. Theconcentration of calcium salt solution which causes maximum proteinsolubilization varies depending on the salt concerned. It is usuallypreferred to utilize a concentration value less than about 1.0 M, andmore preferably a value of about 0.10 to about 0.15 M.

In a batch process, the salt solubilization of the protein is effectedat a temperature of from about 1° C. to about 100° C., preferably about15° to about 65° C., more preferably about 50° C. to about 60° C.,preferably accompanied by agitation to decrease the solubilization time,which is usually about 1 to about 60 minutes. It is preferred to effectthe solubilization to extract substantially as much protein from the soyprotein source as is practicable, so as to provide an overall highproduct yield.

In a continuous process, the extraction of the soy protein from the soyprotein source is carried out in any manner consistent with effecting acontinuous extraction of soy protein from the soy protein source. In oneembodiment, the soy protein source is continuously mixed with thecalcium salt solution and the mixture is conveyed through a pipe orconduit having a length and at a flow rate for a residence timesufficient to effect the desired extraction in accordance with theparameters described herein. In such a continuous procedure, the saltsolubilization step is effected in a time of about 1 to about 60minutes, preferably to effect solubilization to extract substantially asmuch protein from the soy protein source as is practicable. Thesolubilization in the continuous procedure is effected at temperaturesbetween about 1° C. and about 100° C., preferably about 15° to about 65°C., more preferably between about 50° C. and about 60° C.

The extraction is generally conducted at a pH of about 4.5 to about 11,preferably about 5 to about 7. The pH of the extraction system (soyprotein source and calcium salt solution) may be adjusted to any desiredvalue within the range of about 4.5 to about 11 for use in theextraction step by the use of any convenient food grade acid, usuallyhydrochloric acid or phosphoric acid, or food grade alkali, usuallysodium hydroxide, as required.

The concentration of soy protein source in the calcium salt solutionduring the solubilization step may vary widely. Typical concentrationvalues are about 5 to about 15% w/v.

The protein extraction step with the aqueous salt solution has theadditional effect of solubilizing fats which may be present in the soyprotein source, which then results in the fats being present in theaqueous phase.

The protein solution resulting from the extraction step generally has aprotein concentration of about 5 to about 50 g/L, preferably about 10 toabout 50 g/L.

The aqueous calcium salt solution may contain an antioxidant. Theantioxidant may be any convenient antioxidant, such as sodium sulfite orascorbic acid. The quantity of antioxidant employed may vary from about0.01 to about 1 wt % of the solution, preferably about 0.05 wt %. Theantioxidant serves to inhibit oxidation of any phenolics in the proteinsolution.

The mixture of aqueous soy protein solution and residual soy proteinsource may be diluted generally with about 0.5 to about 10 volumes,preferably about 0.5 to about 2 volumes, of aqueous diluent in order todecrease the conductivity of the mixture to a value of generally belowabout 90 mS, preferably about 2 to about 18 mS. Such dilution is usuallyeffected using water, although dilute salt solution, such as sodiumchloride or calcium chloride, having a conductivity of up to about 3 mS,may be used.

The diluent with which the combined soy protein solution and residualsoy protein source is mixed generally has the same temperature as themixture of soy protein solution and residual soy protein source, but thediluent may have a temperature of about 1° to about 100° C., preferablyabout 15° to about 65° C., more preferably about 50° to about 60° C.

The optionally diluted mixture of soy protein solution and residual soyprotein source then is adjusted in pH to a value of about 1.5 to about4.4, preferably about 2 to about 4, by the addition of any suitable foodgrade acid. The acidified mixture has a conductivity of generally belowabout 95 mS for a diluted mixture or generally below about 115 mS for anundiluted mixture, in both cases preferably about 2 to about 23 mS.

The acidified aqueous protein solution is then separated from theresidual soy protein source, in any convenient manner, such as byemploying a decanter centrifuge or any suitable sieve, followed by disccentrifugation and/or filtration, to remove residual soy protein sourcematerial. The separation step is generally conducted at the temperatureof the optionally diluted, pH adjusted mixture of soy protein solutionand residual soy protein material, but may be conducted at anytemperature within the range of about 1° to about 100° C., preferablyabout 15° to about 65° C., more preferably about 50° C. to about 60° C.The separated residual soy protein source may be dried for disposal.Alternatively, the separated residual soy protein source may beprocessed to recover some residual protein. The separated residual soyprotein source may be processed by a conventional isoelectricprecipitation procedure or any other convenient procedure to recoverresidual protein.

Where the soy protein source contains significant quantities of fat, asdescribed in U.S. Pat. Nos. 5,844,086 and 6,005,076, assigned to theassignee hereof and the disclosures of which are incorporated herein byreference, then the defatting steps described therein may be effected onthe aqueous protein solution. Alternatively, defatting of the separatedaqueous protein solution may be achieved by any other convenientprocedure.

The acidified aqueous soy protein solution may be subjected to a heattreatment to inactivate heat labile anti-nutritional factors, such astrypsin inhibitors, present in such solution as a result of extractionfrom the soy protein source material during the extraction step. Such aheating step also provides the additional benefit of reducing themicrobial load. Generally, the protein solution is heated to atemperature of about 70° to about 160° C., for about 10 seconds to about60 minutes, preferably about 80° to about 120° C. for about 10 secondsto about 5 minutes, more preferably about 85° to about 95° C., for about30 seconds to about 5 minutes. The heat treated acidified soy proteinsolution then may be cooled for further processing as described below,to a temperature of about 2° to about 65° C., preferably about 50° C. toabout 60° C.

Alternatively, this heat treatment step may be carried out prior to theseparation of the acidified aqueous protein solution from the residualsoy protein source described above.

The acidified aqueous soy protein solution may be treated with anadsorbent, such as powdered activated carbon or granulated activatedcarbon, to remove colour and/or odour compounds. Such adsorbenttreatment may be carried out under any convenient conditions, generallyat the ambient temperature of the separated aqueous protein solution.For powdered activated carbon, an amount of about 0.025% to about 5%w/v, preferably about 0.05% to about 2% w/v, is employed. The adsorbingagent may be removed from the soy solution by any convenient means, suchas by filtration.

The optionally defatted, optionally heat treated and optionallyadsorbent treated acidified aqueous soy protein solution may optionallybe polished by any convenient means, such as by filtering, to remove anyresidual particulates.

The resulting acidified aqueous soy protein solution may be directlydried to produce a soy protein product. In order to provide a soyprotein product having a decreased impurities content and a reduced saltcontent, such as a soy protein isolate, the acidified aqueous soyprotein solution may be processed prior to drying.

The acidified aqueous soy protein solution may be concentrated toincrease the protein concentration thereof while maintaining the ionicstrength thereof substantially constant. Such concentration generally iseffected to provide a concentrated soy protein solution having a proteinconcentration of about 50 to about 300 g/L, preferably about 100 toabout 200 g/L.

The concentration step may be effected in any convenient mannerconsistent with batch or continuous operation, such as by employing anyconvenient selective membrane technique, such as ultrafiltration ordiafiltration, using membranes, such as hollow-fibre membranes orspiral-wound membranes, with a suitable molecular weight cut-off, suchas about 3,000 to about 1,000,000 Daltons, preferably about 5,000 toabout 100,000 Daltons, having regard to differing membrane materials andconfigurations, and, for continuous operation, dimensioned to permit thedesired degree of concentration as the aqueous protein solution passesthrough the membranes.

As is well known, ultrafiltration and similar selective membranetechniques permit low molecular weight species to pass therethroughwhile preventing higher molecular weight species from so doing. The lowmolecular weight species include not only the ionic species of the foodgrade salt but also low molecular weight materials extracted from thesource material, such as carbohydrates, pigments, low molecular weightproteins and anti-nutritional factors, such as trypsin inhibitors, whichare themselves low molecular weight proteins. The molecular weightcut-off of the membrane is usually chosen to ensure retention of asignificant proportion of the protein in the solution, while permittingcontaminants to pass through having regard to the different membranematerials and configurations.

The concentrated soy protein solution then may be subjected to adiafiltration step using water or a dilute saline solution. Thediafiltration solution may be at its natural pH or at a pH equal to thatof the protein solution being diafiltered or at any pH value in between.Such diafiltration may be effected using from about 1 to about 40volumes of diafiltration solution, preferably about 2 to about 25volumes of diafiltration solution. In the diafiltration operation,further quantities of contaminants are removed from the aqueous soyprotein solution by passage through the membrane with the permeate. Thispurifies the aqueous protein solution and may also reduce its viscosity.The diafiltration operation may be effected until no significant furtherquantities of contaminants or visible colour are present in the permeateor until the retentate has been sufficiently purified so as, when dried,to provide a soy protein isolate with a protein content of at leastabout 90 wt % (N×6.25) d.b. Such diafiltration may be effected using thesame membrane as for the concentration step. However, if desired, thediafiltration step may be effected using a separate membrane with adifferent molecular weight cut-off, such as a membrane having amolecular weight cut-off in the range of about 3,000 to about 1,000,000Daltons, preferably about 5,000 to about 100,000 Daltons, having regardto different membrane materials and configuration.

Alternatively, the diafiltration step may be applied to the acidifiedaqueous protein solution prior to concentration or to the partiallyconcentrated acidified aqueous protein solution. Diafiltration may alsobe applied at multiple points during the concentration process. Whendiafiltration is applied prior to concentration or to the partiallyconcentrated solution, the resulting diafiltered solution may then beadditionally concentrated. The viscosity reduction achieved bydiafiltering multiple times as the protein solution is concentrated mayallow a higher final, fully concentrated protein concentration to beachieved. This reduces the volume of material to be dried.

The concentration step and the diafiltration step may be effected hereinin such a manner that the soy protein product subsequently recoveredcontains less than about 90 wt % protein (N×6.25) d.b., such as at leastabout 60 wt % protein (N×6.25) d.b. By partially concentrating and/orpartially diafiltering the aqueous soy protein solution, it is possibleto only partially remove contaminants. This protein solution may then bedried to provide a soy protein product with lower levels of purity. Thesoy protein product is still able to produce heat stable proteinsolutions under acidic conditions.

An antioxidant may be present in the diafiltration medium during atleast part of the diafiltration step. The antioxidant may be anyconvenient antioxidant, such as sodium sulfite or ascorbic acid. Thequantity of antioxidant employed in the diafiltration medium depends onthe materials employed and may vary from about 0.01 to about 1 wt %,preferably about 0.05 wt %. The antioxidant serves to inhibit theoxidation of any phenolics present in the soy protein solution.

The concentration step and the optional diafiltration step may beeffected at any convenient temperature, generally about 2° to about 65°C., preferably about 50° to about 60° C., and for the period of time toeffect the desired degree of concentration and diafiltration. Thetemperature and other conditions used to some degree depend upon themembrane equipment used to effect the membrane processing, the desiredprotein concentration of the solution and the efficiency of the removalof contaminants to the permeate.

There are two main trypsin inhibitors in soy, namely the Kunitzinhibitor, which is a heat-labile molecule with a molecular weight ofapproximately 21,000 Daltons, and the Bowman-Birk inhibitor, a moreheat-stable molecule with a molecular weight of about 8,000 Daltons. Thelevel of trypsin inhibitor activity in the final soy protein product canbe controlled by manipulation of various process variables.

As noted above, heat treatment of the acidified aqueous soy proteinsolution may be used to inactivate heat-labile trypsin inhibitors. Thepartially concentrated or fully concentrated acidified aqueous soyprotein solution may also be heat treated to inactivate heat labiletrypsin inhibitors. When the heat treatment is applied to the partiallyconcentrated acidified aqueous soy protein solution, the resulting heattreated solution may then be additionally concentrated.

In addition, the concentration and/or diafiltration steps may beoperated in a manner favorable for removal of trypsin inhibitors in thepermeate along with the other contaminants. Removal of the trypsininhibitors is promoted by using a membrane of larger pore size, such asabout 30,000 to about 1,000,000 Da, operating the membrane at elevatedtemperatures, such as about 30° to about 65° C., preferably 50° to about60° C. and employing greater volumes of diafiltration medium, such asabout 10 to about 40 volumes.

Preparing and membrane processing the protein solution at a lower pH ofabout 1.5 to about 3 may reduce the trypsin inhibitor activity relativeto preparing and processing the solution at higher pH of about 3 toabout 4.4. When the protein solution is concentrated and diafiltered atthe low end of the pH range, it may be desired to raise the pH of theretentate prior to drying. The pH of the concentrated and diafilteredprotein solution may be raised to the desired value, for example pH 3,by the addition of any convenient food grade alkali such as sodiumhydroxide.

Further, a reduction in trypsin inhibitor activity may be achieved byexposing soy materials to reducing agents that disrupt or rearrange thedisulfide bonds of the inhibitors. Suitable reducing agents includesodium sulfite, cysteine and N-acetylcysteine.

The addition of such reducing agents may be effected at various stagesof the overall process. The reducing agent may be added with the soyprotein source material in the extraction step, may be added to theaqueous soy protein solution following removal of residual soy proteinsource material, may be added to the concentrated protein solutionbefore or after diafiltration or may be dry blended with the dried soyprotein product. The addition of the reducing agent may be combined witha heat treatment step and the membrane processing steps, as describedabove.

If it is desired to retain active trypsin inhibitors in the concentratedprotein solution, this can be achieved by eliminating or reducing theintensity of the heat treatment step, not utilizing reducing agents,operating the concentration and diafiltration steps at the higher end ofthe pH range, such as pH 3 to about 4.4, utilizing a concentration anddiafiltration membrane with a smaller pore size, operating the membraneat lower temperatures and employing fewer volumes of diafiltrationmedium.

The concentrated and optionally diafiltered protein solution may besubject to a further defatting operation, if required, as described inU.S. Pat. Nos. 5,844,086 and 6,005,076. Alternatively, defatting of theconcentrated and optionally diafiltered protein solution may be achievedby any other convenient procedure.

The concentrated and optionally diafiltered aqueous protein solution maybe treated with an adsorbent, such as powdered activated carbon orgranulated activated carbon, to remove colour and/or odour compounds.Such adsorbent treatment may be carried out under any convenientconditions, generally at the ambient temperature of the concentratedprotein solution. For powdered activated carbon, an amount of about0.025% to about 5% w/v, preferably about 0.05% to about 2% w/v, isemployed. The adsorbent may be removed from the soy protein solution byany convenient means, such as by filtration.

The concentrated and optionally diafiltered aqueous soy protein solutionmay be dried by any convenient technique, such as spray drying or freezedrying. A pasteurization step may be effected on the soy proteinsolution prior to drying. Such pasteurization may be effected under anydesired pasteurization conditions. Generally, the concentrated andoptionally diafiltered soy protein solution is heated to a temperatureof about 55° to about 70° C., preferably about 60° to about 65° C., forabout 30 seconds to about 60 minutes, preferably about 10 minutes toabout 15 minutes. The pasteurized concentrated soy protein solution thenmay be cooled for drying, preferably to a temperature of about 25° toabout 40° C.

The dry soy protein product has a protein content in excess of about 60wt % (N×6.25) d.b. Preferably, the dry soy protein product is an isolatewith a high protein content, in excess of about 90 wt % protein,preferably at least about 100 wt % (N×6.25) d.b.

The soy protein product produced herein is soluble in an acidic aqueousenvironment, making the product ideal for incorporation into beverages,both carbonated and uncarbonated, to provide protein fortificationthereto. Such beverages have a wide range of acidic pH values, rangingfrom about 2.5 to about 5. The soy protein product provided herein maybe added to such beverages in any convenient quantity to provide proteinfortification to such beverages, for example, at least about 5 g of thesoy protein per serving. The added soy protein product dissolves in thebeverage and remains dissolved after thermal processing. The soy proteinproduct may be blended with dried beverage prior to reconstitution ofthe beverage by dissolution in water. In some cases, modification to thenormal formulation of the beverages to tolerate the composition of theinvention may be necessary where components present in the beverage mayadversely affect the ability of the composition of the invention toremain dissolved in the beverage.

EXAMPLES Example 1

This Example illustrates the production of a novel soy protein isolateby the method of the invention.

30 kg of defatted soy white flake was added to 300 L of 0.15 M CaCl₂solution at ambient temperature and agitated for 30 minutes to providean aqueous protein solution. 300 L of reverse osmosis (RO) purifiedwater was added and the pH of the system lowered to about 3 with asolution of HCl. The residual soy white flake was then removed and theresulting protein solution clarified by centrifugation and filtration toprovide 520 L of acidified protein solution having a protein content of1.63% by weight. The acidified solution was heat treated at 90° C. for30 seconds then cooled to 30° C. for further processing.

The heat treated acidified protein solution was reduced in volume from520 L to 141 L by concentration on a polyethersulfone membrane, having amolecular weight cutoff of 100,000 Daltons, operated at a temperature ofapproximately 30° C. At this point the protein solution, with a proteincontent of 5.02 wt %, was diafiltered with 212 L of RO water, with thediafiltration operation conducted at approximately 30° C. Thediafiltered solution was then further concentrated to a volume of 71 L.An aliquot of 31 L of the concentrated protein solution was diafilteredwith an additional 225 L of RO water, with the diafiltration operationconducted at approximately 29° C. After this second diafiltration, theprotein solution was concentrated from a protein content of 10.12% byweight to a protein content of 12.05% by weight then diluted to aprotein content of 6.04% by weight with water to facilitate spraydrying. The protein solution before spray drying was recovered in ayield of 38.6 wt % of the initial filtered protein solution. Thediafiltered, concentrated and diluted protein solution was then dried toyield a product found to have a protein content of 97.40% (N×6.25) d.b.The product was given designation S017-D12-10A S704H.

A solution of S017-D12-10A S704H was prepared by dissolving sufficientprotein powder to supply 0.48 g of protein in 15 ml of reverse osmosispurified water and the colour and clarity assessed using a HunterLabColorQuest XE instrument operated in transmission mode. The pH of thesolution was measured with a pH meter.

The pH, colour and clarity values are set forth in the following Table1:

TABLE 1 pH and HunterLab readings for 3.2% protein solution ofS017-D12-10A S704H Sample pH L* a* b* haze (%) S017-D12-10A S704H 3.2589.24 0.58 16.27 27.9

As may be seen from Table 1, the solution of S017-D12-10A S704H in waterwas semi-transparent, not transparent.

The colour of the dry powder was also assessed with the HunterLabColorQuest XE instrument in reflectance mode. The colour values are setforth in the following Table 2:

TABLE 2 HunterLab scores for S017-D12-10A S704H dry powder Sample L* a*b* S017-D12-10A S704H 88.74 −0.29 8.38

As may be seen from Table 2, the dry product was very light in colour.

Example 2

This Example contains an evaluation of the heat stability in water ofthe soy protein isolate produced by the method of Example 1.

A solution of S017-D12-10A S704H was prepared by dissolving sufficientprotein powder to supply 1.6 g of protein in 80 ml of reverse osmosispurified water. The pH of the solution was determined to be 3.37. Thesample was split into two portions and the pH of one portion was loweredto 3.00 with HCl solution. The clarity of the control and pH adjustedsolutions was assessed by haze measurement with the HunterLab ColorQuestXE instrument. The solutions were then heated to 95° C., held at thistemperature for 30 seconds and then immediately cooled to roomtemperature in an ice bath. The clarity of the heat treated solutionswas then measured again.

The clarity of the protein solutions before and after heating is setforth in the following Table 3:

TABLE 3 Effect of heat treatment on clarity of S017-D12-10A S704Hsolutions Sample Haze before heating (%) Haze after heating (%) pH 3.3755.5 25.2 pH 3.00 38.5 16.9

As can be seen from the results in Table 3, it was found that theinitial solutions of S017-D12-10A S704H were quite hazy, particularly atthe natural pH. However, the solutions were heat stable, with the hazelevel actually reduced somewhat by the heat treatment.

Example 3

This Example contains an evaluation of the solubility in water of thesoy protein isolate produced by the method of Example 1. Solubility wastested based on protein solubility (termed protein method, a modifiedversion of the procedure of Morr et al., J. Food Sci. 50:1715-1718) andtotal product solubility (termed pellet method).

Sufficient protein powder to supply 0.5 g of protein was weighed into abeaker and then a small amount of reverse osmosis (RO) purified waterwas added and the mixture stirred until a smooth paste formed.Additional water was then added to bring the volume to approximately 45ml. The contents of the beaker were then slowly stirred for 60 minutesusing a magnetic stirrer. The pH was determined immediately afterdispersing the protein and was adjusted to the appropriate level (2, 3,4, 5, 6 or 7) with diluted NaOH or HCl. A sample was also prepared atnatural pH. For the pH adjusted samples, the pH was measured andcorrected periodically during the 60 minutes stirring. After the 60minutes of stirring, the samples were made up to 50 ml total volume withRO water, yielding a 1% w/v protein dispersion. The protein content ofthe dispersions was measured using a Leco TruSpec N NitrogenDeterminator. Aliquots (20 ml) of the dispersions were then transferredto pre-weighed centrifuge tubes that had been dried overnight in a 100°C. oven then cooled in a desiccator and the tubes capped. The sampleswere centrifuged at 7,800 g for 10 minutes, which sedimented insolublematerial and yielded a clear supernatant. The protein content of thesupernatant was measured by Leco analysis and then the supernatant andthe tube lids were discarded and the pellet material dried overnight inan oven set at 100° C. The next morning the tubes were transferred to adesiccator and allowed to cool. The weight of dry pellet material wasrecorded. The dry weight of the initial protein powder was calculated bymultiplying the weight of powder used by a factor of ((100−moisturecontent of the powder (%))/100). Solubility of the product was thencalculated two different ways:Solubility (protein method) (%)=(% protein in supernatant/% protein ininitial dispersion)×100  1)Solubility (pellet method) (%)=(1−(weight dry insoluble pelletmaterial/((weight of 20 ml of dispersion/weight of 50 ml ofdispersion)×initial weight dry protein powder)))×100  2)

The natural pH value of the protein isolate produced in Example 1 inwater (1% protein) is shown in Table 4:

TABLE 4 Natural pH of S017-D12-10A S704H solution prepared in water at1% protein Batch Product Natural pH S017-D12-10A S704H 3.43

The solubility results obtained are set forth in the following Tables 5and 6:

TABLE 5 Solubility of S017-D12-10A S704H at different pH values based onprotein method Solubility (protein method) (%) Batch Product pH 2 pH 3pH 4 pH 5 pH 6 pH 7 Nat. pH S017- S704H 98.6 99.5 53.5 2.6 12.5 74.585.4 D12-10A

TABLE 6 Solubility of S017-D12-10A S704H at different pH values based onpellet method Solubility (pellet method) (%) Batch Product pH 2 pH 3 pH4 pH 5 pH 6 pH 7 Nat. pH S017- S704H 98.6 93.2 60.4 2.4 21.5 68.4 79.8D12-10A

As can be seen from the results of Tables 5 and 6, the S704H product wasextremely soluble at pH 2 and also very soluble at pH 3. The product wasnot as soluble at higher pH values.

Example 4

This Example contains an evaluation of the clarity in water of the soyprotein isolate produced by the method of Example 1.

The clarity of the 1% w/v protein solutions prepared as described inExample 3 was assessed by measuring the absorbance at 600 nm (waterblank), with a lower absorbance score indicating greater clarity.Analysis of the samples on a HunterLab ColorQuest XE instrument intransmission mode also provided a percentage haze reading, anothermeasure of clarity.

The clarity results are set forth in the following Tables 7 and 8:

TABLE 7 Clarity of S017-D12-10A S704H solution at different pH values asassessed by A600 A600 Batch Product pH 2 pH 3 pH 4 pH 5 pH 6 pH 7 Nat.pH S017- S704H 0.119 0.140 1.172 2.810 2.391 0.327 0.211 D12-10A

TABLE 8 Clarity of S017-D12-10A S704H solution at different pH values asassessed by HunterLab analysis HunterLab haze reading (%) Batch ProductpH 2 pH 3 pH 4 pH 5 pH 6 pH 7 Nat. pH S017- S704H 22.2 27.3 94.3 97.397.4 71.6 43.5 D12-10A

As can be seen from the results of Tables 7 and 8, the solutions ofS704H were hazy at pH 2 to 3 and cloudier at higher pH values,particularly in the range of 4 to 6.

Example 5

This Example contains an evaluation of the solubility in a soft drink(Sprite) and sports drink (Orange Gatorade) of the soy protein isolateproduced by the method of Example 1. The solubility was determined withthe protein added to the beverages with no pH correction and again withthe pH of the protein fortified beverages adjusted to the level of theoriginal beverages.

When the solubility was assessed with no pH correction, a sufficientamount of protein powder to supply 1 g of protein was weighed into abeaker and a small amount of beverage was added and stirred until asmooth paste formed. Additional beverage was added to bring the volumeto 50 ml, and then the solutions were stirred slowly on a magneticstirrer for 60 minutes to yield a 2% protein w/v dispersion. The proteincontent of the samples was analyzed using a Leco TruSpec N NitrogenDeterminator then an aliquot of the protein containing beverages wascentrifuged at 7,800 g for 10 minutes and the protein content of thesupernatant measured.Solubility (%)=(% protein in supernatant/% protein in initialdispersion)×100

When the solubility was assessed with pH correction, the pH of the softdrink (Sprite) (3.43) and sports drink (Orange Gatorade) (3.09) withoutprotein was measured. A sufficient amount of protein powder to supply 1g of protein was weighed into a beaker and a small amount of beveragewas added and stirred until a smooth paste formed. Additional beveragewas added to bring the volume to approximately 45 ml, and then thesolutions were stirred slowly on a magnetic stirrer for 60 minutes. ThepH of the protein containing beverages was determined immediately afterdispersing the protein and was adjusted to the original no-protein pHwith HCl or NaOH as necessary. The pH was measured and correctedperiodically during the 60 minutes stirring. After the 60 minutes ofstirring, the total volume of each solution was brought to 50 ml withadditional beverage, yielding a 2% protein w/v dispersion. The proteincontent of the samples was analyzed using a Leco TruSpec N NitrogenDeterminator then an aliquot of the protein containing beverages wascentrifuged at 7,800 g for 10 minutes and the protein content of thesupernatant measured.Solubility (%)=(% protein in supernatant/% protein in initialdispersion)×100

The results obtained are set forth in the following Table 9:

TABLE 9 Solubility of S017-D12-10A S704H in Sprite and Orange GatoradeNo pH correction pH correction Solubility Solubility Solubility (%) inSolubility (%) in (%) Orange (%) Orange Batch Product in Sprite Gatoradein Sprite Gatorade S017-D12-10A S704H 73.3 80.7 87.2 84.1

As can be seen from the results of Table 9, the S704H was fairly solublein the Sprite and the Orange Gatorade. The solubility was somewhatimproved by lowering the pH of the protein fortified sample to that ofthe original beverage without protein.

Example 6

This Example contains an evaluation of the clarity in a soft drink andsports drink of the soy protein isolate produced by the method ofExample 1.

The clarity of the 2% w/v protein dispersions prepared in soft drink(Sprite) and sports drink (Orange Gatorade) in Example 5 were assessedusing the HunterLab haze method described in Example 4.

The results obtained are set forth in the following Table 10:

TABLE 10 HunterLab haze readings for S017-D12-10A S704H in Sprite andOrange Gatorade no pH correction pH correction haze haze (%) in hazehaze (%) in (%) in Orange (%) in Orange Batch Product Sprite GatoradeSprite Gatorade no protein 0.0 76.6 0.0 76.6 S017-D12-10A S704H 75.989.8 81.8 87.9

As can be seen from the results of Table 10 the solutions of proteinfortified Sprite and Orange Gatorade were quite cloudy.

Example 7

This Example contains an evaluation of the phytic acid content of thesoy protein isolate produced by the method of Example 1.

The phytic acid content of the S017-D12-10A S704H was determined by theprocedure of Latta and Eskin (J. Agric. Food Chem., 28: 1313-1315). Thephytic acid content of the S017-D12-10A S704H was 1.54 wt % d.b.

SUMMARY OF THE DISCLOSURE

In summary of this disclosure, the present invention provides aprocedure for the preparation of a soy protein product in which the soyprotein source material is not separated from the aqueous soy proteinsolution until after dilution and acidification. Modifications arepossible within the scope of this invention.

What we claim is:
 1. A process of producing a soy protein product havinga protein content of at least about 60 wt % (N×6.25) on a dry weightbasis (d.b.), which comprises: (a) extracting a soy protein source,selected from the group consisting of soymeal, soy flakes, soy grits andsoy flour with an aqueous calcium chloride solution to causesolubilization of soy protein from the soy protein source and to form amixture of aqueous soy protein solution and residual soy protein source,wherein said aqueous calcium chloride solution has a concentration ofabout 0.10 to about 0.15 M and said mixture having a pH of about 4.5 toabout 11; (b) optionally diluting the mixture of aqueous soy proteinsolution and residual soy protein source, (c) subjecting the mixture ofaqueous soy protein solution and residual soy protein source to a pHadjustment step to a pH of about 1.5 to about 4.4 to provide a mixtureof an acidified aqueous soy protein solution and residual soy proteinsource, (d) separating the acidified aqueous soy protein solution fromthe residual soy protein source, (e) concentrating the acidified aqueoussoy protein solution while maintaining the ionic strength substantiallyconstant using a selective membrane technique to form a concentrated soyprotein solution, (f) optionally diafiltering the concentrated soyprotein solution, wherein said concentration step and optionaldiafiltration step are effected until the concentrated and optionallydiafiltered soy protein solution has been sufficiently purified so as,when dried, to provide a soy protein product with a protein source of atleast about 60 wt % (N×6.25) d.b., and (g) drying the optionallydiafiltered and concentrated soy protein solution to provide a soyprotein product having a soy protein content of at least about 60 wt %(N×6.25) d.b., and (g) drying the optionally diafiltered andconcentrated soy protein solution to provide a soy protein producthaving a soy protein content of at least about 60 wt % (N×6.25) d.b. 2.The process of claim 1 wherein said extraction step is effected using anaqueous calcium chloride solution having a concentration of less thanabout 1.0 M.
 3. The process of claim 1 wherein said extraction step iseffected et a temperature of about 15° to about 65° C.
 4. The process ofclaim 1 wherein said aqueous soy protein solution has a proteinconcentration of about 5 to about 50 g/L.
 5. The process of claim 1wherein said aqueous calcium salt solution contains an antioxidant. 6.The process of claim 1 wherein, following said extraction step and priorto said pH adjustment step, said mixture of aqueous soy protein solutionand residual soy protein source is diluted to a conductivity of lessthan about 90 mS.
 7. The process of claim 6 wherein said mixture ofaqueous soy protein solution and residual soy protein source is dilutedwith about 0.5 to about 10 volumes of aqueous diluent.
 8. The process ofclaim 7 wherein said mixture of aqueous soy protein solution andresidual soy protein source is diluted with about 0.5 to about 2 volumesof aqueous diluent.
 9. The process of claim 6 wherein said mixture ofaqueous soy protein solution and residual soy protein source is dilutedto a conductivity of about 2 to about 18 mS.
 10. The process of claim 6wherein said aqueous diluent has a temperature of about 15° to about 65°C.
 11. The process of claim 1 wherein the pH of said optionally dilutedmixture of aqueous soy protein solution and residual soy protein sourceis adjusted to about pH 2 to about
 4. 12. The process of claim 1 whereinsaid acidified mixture of soy protein solution and residual soy proteinsource has a conductivity of less than about 95 mS.
 13. The process ofclaim 1 wherein the acidified mixture of soy protein solution andresidual soy protein source, prior to said separating step is subjectedto a heat treatment step to inactivate heat-labile trypsin inhibitors.14. The process of claim 13, wherein said heat treatment is effected ata temperature of about 70° to about 160° C. for about 10 seconds toabout 60 minutes.
 15. The process of claim 13 wherein the heat treatedacidified mixture of soy protein solution and residual soy proteinsource is cooled to a temperature of about 2° to about 65° C. forfurther processing.
 16. The process of claim 1, wherein following saidseparation step, the acidified aqueous protein solution is subjected toa heat treatment step to inactivate heat-labile, including heat-labiletrypsin inhibitors, and also preferably pasteurizes the acidifiedaqueous protein solution.
 17. The process of claim 16, wherein said heattreatment is effected at a temperature of about 70° to about 160° C. forabout 10 seconds to about 60 minutes.
 18. The process of claim 16wherein the heat treated acidified soy protein solution is cooled to atemperature of about 2° to about 65° C. for further processing.
 19. Theprocess of claim 1 wherein following said separating step, the acidifiedaqueous soy protein solution is treated with an adsorbent to removecolour and/or odour compounds from the acidic aqueous soy proteinsolution.
 20. The process of claim 1 wherein the acidified aqueous soyprotein solution is subjected to a polishing step.
 21. The process ofclaim 1 wherein said acidified aqueous soy protein solution isconcentrated while maintaining the ionic strength thereof substantiallyconstant to produce a concentrated acidified soy protein solution havinga protein concentration of about 50 to about 300 g/L.
 22. The process ofclaim 21 wherein said concentrated acidified aqueous soy proteinsolution has a protein concentration of about 100 to about 200 g/L. 23.The process of claim 21 wherein said concentration step is effected byultrafiltration using a membrane having a molecular weight cut-off ofabout 3,000 to about 1,000,000 daltons.
 24. The process of claim 21wherein a diafiltration step is effected using water, acidified water,dilute saline or acidified dilute saline on the acidified soy proteinsolution before or after partial or complete concentration thereof. 25.The process of claim 24 wherein said diafiltration is effected usingabout 1 to about 40 volumes of diafiltration solution.
 26. The processof claim 24 wherein said diafiltration is effected until no significantfurther quantities of contaminants or visible colour are present in thepermeate.
 27. The process of claim 24 wherein said diafiltration iseffected until the retentate has been sufficiently purified so as, whendried, to provide a soy protein isolate with a protein content of atleast about 90 wt % (N×6.25) d.b.
 28. The process of claim 24 whereinsaid diafiltration is effected using a membrane having a molecularweight cut-off of about 3,000 to about 1,000,000 Daltons.
 29. Theprocess of claim 21 wherein said concentration step and optionaldiafiltration step are carried out at a temperature of about 2° to about65° C.
 30. The process of claim 21 wherein partially concentrated orconcentrated and optionally diafiltered acidified aqueous soy proteinsolution is subjected to a heat treatment step to inactivate heat-labiletrypsin inhibitors.
 31. The process of claim 30 wherein said heattreatment is effected at a temperature of about 70° to about 160° C. forabout 10 seconds to about 60 minutes.
 32. The process of claim 30wherein the heat treated soy protein solution is cooled to a temperatureof about 2° to about 65° C. for further processing.
 33. The process ofclaim 21 wherein said concentrated and optionally diafiltered acidifiedaqueous soy protein solution is treated with an adsorbent to removecolour and/or odour compounds.
 34. The process of claim 21 wherein saidconcentrated and optionally diafiltered acidified aqueous soy proteinsolution is pasteurized prior to drying.
 35. The process of claim 34wherein said pasteurization step is effected at a temperature of about55° to about 70° C. for about 30 seconds to about 60 minutes.
 36. Theprocess of claim 27 wherein said concentrated and diafiltered acidifiedaqueous soy protein solution is dried to provide a soy protein isolatehaving a protein content of at least about 90 wt % (N×6.25) d.b.
 37. Theprocess of claim 36 wherein said soy protein isolate has a proteincontent of at least about 100 wt % (N×6.25) d.b.
 38. The process ofclaim 21 wherein the concentration and/or optional diafiltration stepare operated in a manner favourable to the removal of trypsininhibitors.
 39. The process of claim 1 wherein a reducing agent ispresent during the extraction step to disrupt or rearrange the disulfidebonds of trypsin inhibitors to achieve a reduction in trypsin inhibitoractivity.
 40. The process of claim 21 wherein a reducing agent ispresent during the concentration and/or optional diafiltration step todisrupt or rearrange the disulfide bonds of trypsin inhibitors toachieve a reduction in trypsin inhibitor activity.
 41. The process ofclaim 1 wherein a reducing agent is added to the concentrated andoptionally diafiltered soy protein solution prior to drying and/or thedried soy protein product to disrupt or rearrange the disulfide bonds oftrypsin inhibitors to achieve a reduction in trypsin inhibitor activity.42. The process of claim 3 wherein said extraction step is effected at atemperature of about 50° to about 60° C.
 43. The process of claim 1wherein said extraction with aqueous calcium salt solution is conductedat a pH of about 5 to about
 7. 44. The process of claim 4 wherein saidaqueous soy protein solution has a protein concentration of about 10 toabout 50 g/L.
 45. The process of claim 10 wherein said aqueous diluenthas a temperature of about 50° to about 60° C.
 46. The process of claim12 wherein said acidified of soy protein solution and residual soyprotein source has a conductivity of about 2 to about 23 mS.
 47. Theprocess of claim 14 wherein said heat treatment is effected at atemperature of about 80° to about 120° C. for 10 seconds to about 5minutes.
 48. The process of claim 15 wherein the heat treated acidifiedmixture of soy protein solution and residual soy protein source iscooled to about 50° to about 60° C. for further processing.
 49. Theprocess of claim 17 wherein the heat treatment is effected at atemperature of about 80° to about 120° C. for about 10 seconds to about5 minutes.
 50. The process of claim 18 wherein the heat treatedacidified soy protein solution is cooled to a temperature of about 50 toabout 60° C. for further processing.
 51. The process of claim 21 whereinsaid membrane has a molecular weight cut-off of about 5,000 to about100,000 Daltons.
 52. The process of claim 25 wherein said diafiltrationis effected using about 2 to about 25 volumes of diafiltration solution.53. The process of claim 28 wherein the membrane has a molecular weightcut-off of about 5,000 to about 100,000 Daltons.
 54. The process ofclaim 29 wherein said concentration and optional diafiltration step arecarried out at a temperature of about 50° to about 60° C.
 55. Theprocess of claim 31 wherein said heat treatment is effected at atemperature of about 80 to about 120° C. for about 10 second to about 5minutes.
 56. The process of claim 32 wherein the heat treated soyprotein solution is cooled to a temperature of about 50 to about 60° C.for further processing.
 57. The process of claim 35 wherein saidpasteurization step is effected at a temperature of about 60° to about65° C. for about 10 to about 15 minutes.